Weather vs. Climate

Weather – current state of the atmosphere
Climate – aggregate atmospheric conditions; long-term average weather

Temperature

How do we measure global temperature?
What is the problem with using thermometers for measuring long term average temperature?
Limited span of time: first thermometer invented:

Global Temperature

Average of all temperature record measurements. Historical records Municipal/state/federal records Amateur records and diaries How do we get data from before 1611?

Proxy Temperature Records

Data from sources which do not give actual temp. – provide an inferred temperature
Biological Proxy Records: tree rings, pollen, floral and faunal distributions, fossils
Geological Proxy Records: sediment/glacial deposits, ice cores, minerals, geochemistry
Chemical Proxy Records: O¹⁸/O¹⁶ ratios (ice and foram shells)

Sea-Level Measurements

Sea level is not constant
Changes on a daily basis:
Changes on an annual basis:

Sea-Level Changes

Causes of eustatic changes in sea level:
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Global Warming!!!

Is the world actually getting warmer?
“Warming of the climate system is unequivocal… The atmosphere and oceans have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentration of greenhouse gases have increased.” – IPCC 2013: Climate Change 2013: The Physical Science Basis.

The Evidence of Global Warming

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Ten Signs of a Warming World - NOAA web site

Temperature

Average Global Temperature, 1880 to 2018
Benthic Foraminiferal Stable Isotope Data Graph: 1 million b.p. to Present
Mean Global Temperature: 4.6 billion b.p. to Present

Ice

Global Glacier Mass Balance: 1961 to 2009
Mean Specific Alpine Glacial Mass Balance
Grinnell Glacier
Red Eagle and Logan Glaciers

Ocean Temperature

Average Global Ocean Surface Temperature, 1880 to 2018

Sea Level

Average Annual Global Mean Sea Level: 1880 to 2014

The Evidence - Summary

Causes of Climate Change

Natural Causes or Human Induced Causes?

Solar Radiation:
Main energy source at Earth's surface.
Driving force for:
Changes in amounts of incoming vs. outgoing radiation will result in global warming or cooling.
Factors controlling amount of insolation:

Orbital Parameters

Surface insolation variations due to orbital parameter variations.
1) Axial tilt
2) Precession
3) Orbital Eccentricity

Milankovitch Cycles

Cycles in amount of solar radiation received at surface due to orbital variations.

Greenhouse Effect

A system in which shortwave radiation is allowed to enter freely and is absorbed, then is re-radiated as longwave radiation. The longwave radiation is then retained within the system.
Important greenhouse gases:
     H₂O Water
     CO₂ Carbon Dioxide
     CH₄ Methane
     Nitrous oxide (N₂O)
     Ozone (O₃)
     Chlorofluorocarbons (CFCs)
     Hydrofluorocarbons (HFCs)

Greenhouse Gases

CO₂ Carbon Dioxide
CH₄ Methane

Future Predictions

Projected Future Global Temperature, Present to 2100
Projected Future Global Sea Level, Present to 2100
Average Projected Changes in Precipitation: 2080 to 2099

Additional Information

Global Warming: A Short Discourse

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